import collections
from itertools import combinations

from migen.fhdl.structure import *
from migen.fhdl.structure import _Fragment
from migen.fhdl.specials import Special
from migen.fhdl.tools import flat_iteration, rename_clock_domain

class FinalizeError(Exception):
	pass

def _flat_list(e):
	if isinstance(e, collections.Iterable):
		return flat_iteration(e)
	else:
		return [e]

class _ModuleProxy:
	def __init__(self, fm):
		object.__setattr__(self, "_fm", fm)

class _ModuleComb(_ModuleProxy):
	def __iadd__(self, other):
		self._fm._fragment.comb += _flat_list(other)
		return self

def _cd_append(d, key, statements):
	try:
		l = d[key]
	except KeyError:
		l = []
		d[key] = l
	l += _flat_list(statements)

class _ModuleSyncCD:
	def __init__(self, fm, cd):
		self._fm = fm
		self._cd = cd

	def __iadd__(self, other):
		_cd_append(self._fm._fragment.sync, self._cd, other)
		return self

class _ModuleSync(_ModuleProxy):
	def __iadd__(self, other):
		_cd_append(self._fm._fragment.sync, "sys", other)
		return self

	def __getattr__(self, name):
		return _ModuleSyncCD(self._fm, name)

	def __setattr__(self, name, value):
		if not isinstance(value, _ModuleSyncCD):
			raise AttributeError("Attempted to assign sync property - use += instead")

# _ModuleForwardAttr enables user classes to do e.g.:
# self.subm.foobar = SomeModule()
# and then access the submodule with self.foobar.
class _ModuleForwardAttr:
	def __setattr__(self, name, value):
		self.__iadd__(value)
		setattr(self._fm, name, value)

class _ModuleSpecials(_ModuleProxy, _ModuleForwardAttr):
	def __iadd__(self, other):
		self._fm._fragment.specials |= set(_flat_list(other))
		return self

class _ModuleSubmodules(_ModuleProxy):
	def __setattr__(self, name, value):
		self._fm._submodules += [(name, e) for e in _flat_list(value)]
		setattr(self._fm, name, value)
	
	def __iadd__(self, other):
		self._fm._submodules += [(None, e) for e in _flat_list(other)]
		return self

class _ModuleClockDomains(_ModuleProxy, _ModuleForwardAttr):
	def __iadd__(self, other):
		self._fm._fragment.clock_domains += _flat_list(other)
		return self

class Module:
	def get_fragment(self):
		assert(not self._get_fragment_called)
		self._get_fragment_called = True
		self.finalize()
		return self._fragment

	def __getattr__(self, name):
		if name == "comb":
			return _ModuleComb(self)
		elif name == "sync":
			return _ModuleSync(self)
		elif name == "specials":
			return _ModuleSpecials(self)
		elif name == "submodules":
			return _ModuleSubmodules(self)
		elif name == "clock_domains":
			return _ModuleClockDomains(self)

		# hack to have initialized regular attributes without using __init__
		# (which would require derived classes to call it)
		elif name == "finalized":
			self.finalized = False
			return self.finalized
		elif name == "_fragment":
			try:
				sim = [self.do_simulation]
			except AttributeError:
				sim = []
			self._fragment = _Fragment(sim=sim)
			return self._fragment
		elif name == "_submodules":
			self._submodules = []
			return self._submodules
		elif name == "_clock_domains":
			self._clock_domains = []
			return self._clock_domains
		elif name == "_get_fragment_called":
			self._get_fragment_called = False
			return self._get_fragment_called

		else:
			raise AttributeError("'"+self.__class__.__name__+"' object has no attribute '"+name+"'")

	def __setattr__(self, name, value):
		if name in ["comb", "sync", "specials", "submodules", "clock_domains"]:
			if not isinstance(value, _ModuleProxy):
				raise AttributeError("Attempted to assign special Module property - use += instead")
		else:
			object.__setattr__(self, name, value)

	def _collect_submodules(self):
		r = [(name, submodule.get_fragment()) for name, submodule in self._submodules]
		self._submodules = []
		return r

	def finalize(self, *args, **kwargs):
		if not self.finalized:
			self.finalized = True
			# finalize existing submodules before finalizing us
			subfragments = self._collect_submodules()
			self.do_finalize(*args, **kwargs)
			# finalize submodules created by do_finalize
			subfragments += self._collect_submodules()
			# resolve clock domain name conflicts
			needs_renaming = set()
			for (mod_name1, f1), (mod_name2, f2) in combinations(subfragments, 2):
				f1_names = set(cd.name for cd in f1.clock_domains)
				f2_names = set(cd.name for cd in f2.clock_domains)
				common_names = f1_names & f2_names
				if common_names:
					if mod_name1 is None or mod_name2 is None:
						raise ValueError("Multiple submodules with local clock domains cannot be anonymous")
					if mod_name1 == mod_name2:
						raise ValueError("Multiple submodules with local clock domains cannot have the same name")
				needs_renaming |= common_names
			for mod_name, f in subfragments:
				for cd in f.clock_domains:
					if cd.name in needs_renaming:
						rename_clock_domain(f, cd.name, mod_name + "_" + cd.name)
			# sum subfragments
			for mod_name, f in subfragments:
				self._fragment += f

	def do_finalize(self):
		pass